Apparatus for drying an electrophotographic recording element

ABSTRACT

THE COMBINATION OF TWO ROTATABLY SUPPORTED ROLLS DISPOSED IN PARALLEL CONTACTING RELATIONSHIP WITH ONE ANOTHER SO AS TO FORM A SQUEEGEE NIP, GAS CIRCULATING MEANS, AND, IN SOME EMBODIMENTS, A HEATED ROLL FOR DRYING A LIQUID DEVELOPER CARRIED ON ONE SURFACE OF AN ELECTROPHOTOGRAPHIC RECORDING ELEMENT.

March V15, 1 1 N. L. HAKANSON APPARATUS FOR DRYING AN ELECTROPHOTOGRAPHIC RECORDING ELEMENT Filed Dec. 9. 1968 INVENTOR. Nils L. Hokofison ATT RNEY.

United States Patent 3,570,136 APPARATUS FOR DRYING AN ELECTRO- PHOTOGRAPHIC RECORDING ELEMENT Nils L. Hakanson, West Springfield, Mass., assignor to The Plastic Coating Corporation, Hampden County,

Mass.

Filed Dec. 9, 1968, Ser. No. 782,129 Int. Cl. G03g 13/10 US. 'Cl. 34-114 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION (1) Field of the invention The invention relates to drying apparatus and, more particularly, to apparatus for drying an electrophotographic recording element to one surface of which has been applied a liquid developer to render visible an electrostatic image carried on said front surface.

(2) Background of the invention In the past, copying systems of the electrostatic type have been generally of an intermittent operation involving single sheets or, if of a continuous type, have been quite slow. In either case, due to the slow speed, there has been no serious problem in drying the sheet after a liquid developer has been applied thereto to render the image visible. Such drying could be accomplished by slowly moving the sheet or recording element through a dryer unit which generally involved radiant heat of some type. Occasionally, an air doctor was utilized to initially sweep excess liquid developer from the sheet. Contact of the sheet or recording element was avoided if at all possible so as not to disturb the image being developed. Such images are quite fragile prior to drying or fusion, since they are formed merely of charged particles attracted and held to oppositely-charged portions of the recording element or sheet.

However, with the continuous development processes which have arisen to enable the high-speed copying of data generated perhaps by a computer and often appearing in the form of microfilm, the inability to dry the recording element at high speed has caused serious problems. The old type of apparatus was simply not able to remove the excess liquid developer from the sheet or recording element and to dry the recording element, within the space confines permitted and at the speeds required up to 200 feet per minute and even higher.

It is an object and advantageof the present invention to provide apparatus for drying an electrophotographic recording element to which a liquid developer has been applied.

It is a further object and advantage to provide appara- I SUMMARY OF THE INVENTION The invention is apparatus for drying an electrophotographic recording element to the front surface of which a liquid developer has been applied to render visible an 3,570,136 Patented Mar. 16, 1971 "ice electrostatic images carried on the front surface. The apparatus includes two rotatably supported rolls disposed in parallel contacting relationship with one another so as to form a squeegee nip through which the recording element passes. The rolls serve to remove excess liquid developer from the front surface of the recording element. The apparatus also includes gas circulating means arranged to circulate gas over the front surface of the recording element so as to remove volatile portions of the liquid developer therefrom. In some embodiments, the apparatus also includes a heated roll over which the recording element is entrained during a portion of its treatment by the gas circulating means. The heated roll is adapted to contact the back surface of the recording element, and to impart heat to the recording element to promote removal of volatile portions of the liquid developer.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a side elevation view of one embodiment of apparatus of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawing shows one form of apparatus for applying a liquid developer to the lower or front surface of a continuous recording element 10 which has an electrostatic image on its lower or front surface. This apparatus comprises a tank 11 containing a supply of liquid developer 12 into which the lower surface of the recording element 10 is immersed by means of a backing member 13 positioned above the recording element 10 and the supply of liquid developer 12. The backing member 13 is adapted to press the recording element 10 downwardly into the liquid developer 12. That is, the backing member 13 guides the recording element 10 along a path such that the lower or front surface of the recording element which carries the electrostatic image is immersed in the liquid developer .12 and is thereby rendered visible. Of course, many other ways of applying liquid developer to one surface of the recording element .10 could be employed with good success, such as spray techniques.

The recording element 10 is kept under tension as it passes through the developing apparatus. It is gripped by means of a pressure nip created by rolls 14 and 15 which are biased by braking means (not shown) to cause a slight drag on the recording element 10. In addition, as the recording element 10 emerges from the developing apparatus, it is fed through a squeegee nip 1 6 formed by two rotatably mounted rolls 17 and 18; These rotatably mounted rolls 17 and 1 8 are disposed in parallel contacting relationship with one another and serve to remove excess liquid developer 12 from the lower or front surface of the recording element 10 as it passes through the squeegee nip 16 formed by the rolls 17 and 18. Preferably one of these rolls 17 and 1:8 as driven as by the belt .20 attached to the pulley 21 on the motor 22. The belt 20 drives a pulley 23 on one end of roll 17. This arrangement provides tension in the stretch of the recording element 10 between the drag rolls 14 and 15 and the squeegee rolls 17 and 18. Alternatively, the recording element may be tensioned at a point further along its path beyond the squeegee rolls 17 and 18 and the result would still be the same. That is, the recording element would have its back or upper surface held in firm contact with the backing member 13 of the developing apparatus so as to prevent liquid developer from contacting the back surface of the recording element 10. This arrangement also provides uniform contact of the recording element 10 with the backing member 13 in the event a bias voltage or charge is applied through the backing member 13 to as- 3 sist the developing operation in a manner which is wellknown to those skilled in the art. The roll 17 preferably has a resilient outer surface, and may be made of an elastomeric material such as rubber or may have an outer cover 24 of such material as shown in the drawing.

Following the squeegee rolls 17 and 18 the recording element is entrained over a heated rotatably mounted roll 25. In this manner, heat is transmitted through the back surface of the recording element 10 and serves to heat liquid developer 12 on the front surface thereof and to promote yolatilization of volatile portions of the liquid developer 12. The heated roll 25 may be heated electrically as by the resistance elements 26 (shown schematically) beneath its surface or through the circulation of heated fluid such as steam therethrough. It is preferable that the heated roll 25 be mounted for free rotation but it may also be driven. In some instances it might be stationary with the recording element 10 sliding over it. After leaving the heated roll 25, the recording element 10 is suspended over a short span and entrained over a subsequent guide roll 27 whereupon the drying of the liquid developer 12 is substantially complete and the recording element 10 may be subsequently processed as by folding, stacking, severing, collating or any other desired process.

Gas circulating means, indicated generally by reference number 28, are employed for circulating gas over the front surface of the recording element 10 during the time the recording element is in contact with the heated roll 25 and is suspended between the heated roll 25 and the guide roll 27. The gas circulating means 28 include a hood 30 spaced in close relationship to the front surface of the recording element 10, that is, from about /2 to about 2 inches from the front surface of the recording element 10. Gas such as air at ambient temperature is fed into the downstream end of the hood 30 and is then emitted onto the front surface of the recording element 10 and generally directed along a flow path countercurrent to the direction of movement of the recording element 10 with a primary emission point being in the area between the end of the hood 30 adjacent the heated roll 25 and the squeegee rolls 17 and 18. Of course, portions of the gas are emitted along the sides of the hood 30 between the hood 30 and the recording element 10. The gases containing the volatile portions of the liquid developer 12 are collected in the apparatus and withdrawn from the apparatus through ducts (not shown).

The gases may enter the hood 30 under pressure or may be drawn into it as by a motor driven fan 31 positioned as shown at the inlet end 32 of the hood 30. It is preferred that the gases be heated prior to their circulation over the front surface of the recording element 10. This is conveniently accomplished by employing a plurality of heating means 33 such as electrical heating elements along the bottom of the hood 30 in the portion disposed over the suspended portion of the recording element 10. In this manner, the gases entering the hood 30 are forced to pass these heating elements 33 prior to being emitted into contact with the front surface of the recording element 10 and the heat contained in these gases further assists in the drying of the liquid developer 12. These heating elements 33 also serve to radiate heat onto the front surface of the recording element, thereby further assisting in the drying thereof.

From the above it can be seen that the apparatus of the invention provides means for drying an electrophotographic recording element moving at much higher speeds than has theretofore been the case. Thus the combination of the squeegee rolls with the heated roll and the gas circulating means provides apparatus having higher drying capacity than has heretofore been obtainable. This high drying capacity enables the developing of the record ing element at high speeds while allowing the recording element to be dried in a fairly short distance of travel through the machine which of course is an essential feature of any type of data handling equipment to be utilized in an ofiice.

From the above it can be seen that many changes and modifications can be made in the apparatus described without departing from the spirit and scope of the invention. For example, many different forms of hoods may be used and the heating means employed with such hoods could be quite different from those shown. Therefore, the invention is not intended to be limited to the particular embodiments described above.

What is claimed is:

1. Apparatus for drying an electrophotographic recording element including a liquid developer to render visible an electrostatic image carried on said front surface, said apparatus comprising:

two rotatably supported rolls disposed in parallel contacting relationship with one another so as to form a squeegee nip through which said recording element passes, whereby excess liquid developer is removed from said front surface of said recording element, and

roll means over which said recording element is transported,

gas circulating means following said squeegee nip along the path of said recording element to circulate gas over said front surface of said recording element so as to remove volatile portions of said liquid developer therefrom.

2. Apparatus according to claim 1, wherein said roll means include a heated roll adapted to contact the back surface of said recording element, whereby heat is imparted by said heated roll to said recording element to promote removal of volatile portions of said liquid developer.

3. Apparatus according to claim 1, including radiant heating means for applying radiant heat to said recording element during at least a portion of its treatment by said gas circulating means, whereby heat is imparted to said recording element to promote removal of volatile portions of said liquid developer.

4. Apparatus according to claim 3, wherein said gas circulating means and said heating means elevates the temperature of said gas prior to its circulation over said front surface of said recording element.

5. Apparatus according to claim 1, wherein said gas circulating means include a hood disposed adjacent successive transverse portions of said recording element as it moves along its path following its passage through said squeegee nip.

6. Apparatus according to claim 5, wherein said hood is adapted to receive gas adjacent the point where said recording element leaves said hood, and to move said gas in a direction generally opposite the direction of movement of said recording element past said hood whereby the driest gas contacts the driest portions of the recording element.

References Cited UNITED STATES PATENTS 3,318,017 5/1967 Smith, Jr. 34l16X 2,344,686 3/1944 Fanselow 34-1l4 2,437,254 3/1948 Hill 34-116 3,187,162 6/1965 Hojo et al. 34-41X 3,436,523 4/1969 Umahashi et al 34-11OX 3,447,247 6/ 1969 Daane 34122 MARTIN P. SCHWADRON, Primary Examiner T. W. STREULE, Assistant Examiner US. Cl. X.R. 

